1. Field of the Invention
The present invention relates to a ball transfer unit, and in particular to a ball transfer unit comprising an air entrance passage.
2. The Related Arts
As shown in FIG. 1, a conventional ball transfer unit comprises: a main body 100, a first rotating body 200, and a plurality of second rotating bodies 300 arranged between the main body 100 and the first rotating body 200. The main body 100 has an end forming a receiving chamber 110 and thus forming a receiving chamber sidewall 112. The second rotating bodies 300 are rotatably arranged on the receiving chamber sidewall 112. The main body 100 has an opposite end that forms a connection section 120. The receiving chamber sidewall 112 has a free end forming a stop rim 114 extending to each other for retaining and supporting the second rotating bodies 300. When the ball transfer unit is used in an application where there are a lot of powder dusts, such as a glass substrate cutting machine, the powder dusts may fall into the tiny gap between the first rotating body 200 and the stop rim 114 and converts rolling friction between the first rotating body 200 and the second rotating bodies 300 into sliding friction, thereby increasing the friction force therebetween, affecting the performance of the ball transfer unit and shortening the lifespan of the ball transfer unit.